BBC HD's principal technologist Andy Quested has answered complaints about the quality of the picture by pointing out that lessons are still being learned about filming high definition television.
Responding to a number of complaints, Quested points out that different viewers like different things when it comes to HD, and that some programmes have to carry standard definition sections because of filming limitations.
"Programmes like Amazon will always have sequences where conditions mean no matter how good the broadcast technology, domestic cameras that are always much smaller and less conspicuous will be used to reduce risk to the crew with a resulting loss in picture quality," Quested wrote on the BBC internet blog
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"We are always looking at new technologies that will improve the picture quality in challenging environments but it will take some time before it is uniformly high. In the mean time programmes must limit the amount of standard definition or low quality high definition to 25% of their duration."
"Many of our high definition programmes use the 25 frame progressive standard (film style). I know some people do not like this and think it degrades the resolution of the picture, while others think it contributes to the quality and style of the programme.
"Cranford, Silent Witness, Tess and other dramas are also using the latest large image format cameras. Theses cameras use a single image sensor that is about the same size as a 16:9 35mm film frame and gives the image a very shallow depth of field.
"A shallow depth of field will put all but the key subject out of focus and allows a director to use focus as a story telling tool.
"Again some people think high definition pictures should be pin sharp from the nose of a person in close-up to the trees on the horizon, others find all this visual information distracting and a drama director will use focus to point you to the action they want you to watch."